During the coming year we will investigate: (1) Immune reactivities against a crude cercarial antigenic preparation, including protective responses. (2) The pathogenesis of lesion formation in T lymphocyte-depleted mice. (3) The immune responses to soluble egg antigen (SEA) during chronic infection. (4) The development and nature of glomerular lesions in chronic low-grade infections. (5) The nature of the immunodepressed state of mice harboring heavy initial infections. (6) The physicochemical and immunological nature of SEA. (7) The production of lymphokines, especially ESP, by isolated schistosome granulomas. (8) The types of lymphoid cells which produce ESP. (9) Eosinophilopoesis in the bone marrow schistosomiasis, and in cultures. (10) The physiccochemical and biological character of the lymphokine ESP. (11) The nature of interactions of eosinophils and schistosome eggs.